a. Field of the Invention
The instant invention relates to digital pulse-width modulators and switched mode DC-DC power converters utilizing such pulse-width modulators with feed-forward compensation.
b. Background
Pulse-width-modulation (PWM) is a technique for controlling analog circuits with a digital output. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. PWM is a way of digitally encoding analog signal levels in which a duty cycle of a square wave is modulated to encode a specific analog signal.
In switched-mode power converters, for example, PWM can be used to control a switching cycle of at least one switch of the power converter. A pulse-width-modulator, for example, may be used in an open-loop or closed-loop control scheme to regulate the output of the power converter. With such a control scheme, feed-forward compensation can be used to reduce effects of input voltage disturbances on the converter output voltage and improve steady-state and dynamic responses of the converter.
Digital controllers for DC-DC power converters can provide custom architectures and realizations of building blocks including high-resolution, high-frequency, digital pulse-width modulators (DPWM), simplified discrete-time compensator schemes, and analog-to-digital (A/D) converters. Digital controllers can also. offer advantages of lower sensitivity to parameter variations, programmability, and reduction or elimination of passive components, often without compromising dynamic performance, simplicity, or cost.
While input voltage feed-forward compensation has been used in analog voltage-mode pulse-width modulated controllers, such analog realizations lead to wide process and temperature variations due to parameter values of on-chip passive elements (e.g., resistors and capacitors) and present an important design constraint in terms of chip area and dynamic performance. Analog realizations also require additional analog-to-digital and digital-to-analog converters when used in combination with digital controllers.